Scientists use quantum devices to slow chemical reactions by a factor of 100 billion

What happens in nature in femtoseconds observed in milliseconds?

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Conical intersections are common in chemistry and physics and frequently control functions, including photocatalysis, chemical reactivity, vision, and light harvesting. They serve as conduits between molecular electronic states, enabling quick and effective relaxation during chemical dynamics.

A geometric phase in the molecular wavefunction occurs when a reaction path circles a conical intersection, and this phase can interfere with quantum mechanics to change the reaction’s conclusion. There has yet to be a direct observation of the underlying wavepacket interference in previous experiments. Still, indirect measurements of geometric phases in scattering patterns and spectroscopic observables have been made.

For the first time, scientists at the University of Sydney have used a quantum computer to engineer and directly observe a process critical in chemical reactions by slowing it down by a factor of 100 billion times.

By understanding these basic processes inside and between molecules, scientists can open up a new world of possibilities in materials science, drug design, or solar energy harvesting. It could also help them improve other processes that rely on molecules interacting with light.

The research team specifically observed the interference pattern of a single atom induced by a ‘conical intersection,’ a typical geometric shape in chemistry.

Conical intersections are well-known in chemistry and are essential to quick photochemical reactions like photosynthesis and light-harvesting for human vision.

To do so, they created an experiment using a trapped-ion quantum computer in a completely new way. Using a relatively modest quantum gadget, they were able to create and map this extremely challenging problem, which subsequently allowed them to slow the process down by a factor of 100 billion.

Ms. Olaya Agudelo from the School of Chemistry said, “In nature, the whole process is over within femtoseconds. That’s a billionth of a millionth – or one quadrillionth – of a second. Using our quantum computer, we built a system to slow the chemical dynamics from femtoseconds to milliseconds. This allowed us to make meaningful observations and measurements.”

“This has never been done before.”

Joint lead author Dr Christophe Valahu from the School of Physics said: “Until now, we have been unable to observe the dynamics of ‘geometric phase directly’; it happens too fast to probe experimentally.”

“Using quantum technologies, we have addressed this problem. It is akin to simulating the air patterns around a plane wing in a wind tunnel.”

“Our experiment wasn’t a digital approximation of the process – this was a direct analog observation of the quantum dynamics unfolding at a speed we could observe.”

Co-author and research team leader, Associate Professor Ivan Kassal from the School of Chemistry and the University of Sydney Nano Institute, said“This exciting result will help us better understand ultrafast dynamics – how molecules change at the fastest timescales.

“It is tremendous that at the University of Sydney, we have access to the country’s best programmable quantum computer to conduct these experiments.”

Journal Reference:

  1. Valahu, C.H., Olaya-Agudelo, V.C., MacDonell, R.J. et al. Direct observation of geometric-phase interference in dynamics around a conical intersection. Nat. Chem. (2023). DOI: 10.1038/s41557-023-01300-3